This invention relates to cooling systems for vehicles, and more particularly, to vehicular cooling systems that include a coolant system for an engine coolant of the vehicle and a carbon dioxide (CO2) type air conditioning system.
This application claims priority to German application DE 101 37 907.2, filed Aug. 2, 2001, the entire contents of which are incorporated herein by reference 7.
Vehicular cooling systems that include a coolant system for an engine coolant of the vehicle and a transcritical or CO2 type refrigeration or air conditioning system are know. Typically, the cooling system will include a coolant heat exchanger or radiator, and the CO2 type air conditioning system will include an air conditioning loop consisting of at least a compressor, a gas cooler, an expansion valve, and an evaporator, all connected in series by in-flow and out-flow conduits for the refrigerant, which would typically be CO2. in such air conditioning systems, the refrigerant will typically enter the gas cooler with a temperature of about 150xc2x0 C. and will be cooled to about ambient temperature by a cooling air flow.
It is also known to provide an intermediate heat exchanger in the form of a so called suction line heat exchanger in CO2 type air conditioning systems to transfer heat from the high temperature refrigerant on the high pressure side of the air conditioning system to the low temperature refrigerant on the low pressure side of the system, which will typically at least partially contain a liquid phase. However, because of their function, these types of heat exchangers are arranged on the high pressure side of the system downstream of the gas cooler.
A relatively high inlet temperature of the refrigerant in combination with the high pressures that prevail in CO2 type systems, can cause significant material stresses in the gas cooler, which is typically fabricated of aluminum sheet. This will typically require larger thicknesses for the aluminum sheet and a more pressure-stabile configuration, both of which are cost factors.
One possible solution to the high stresses is to operate the CO2 type air conditioning unit at a lower temperature level. However, operation of such systems at a lower level can lead to inadequate cooling performance or, if inadequate cooling performance is unacceptable, the heat exchangers for the air conditioning system having larger and more efficient heat exchange surfaces, which is typically out of the question for vehicle manufactures who are tending to require increasingly smaller design space for such systems.
Another concern for such systems is that the air conditioning system typically posses a partially unsatisfactory output in the limited load range, and in particular with the many idle phases of the vehicle because the compressor, driven by the motor in such idle phases, can only furnish a relatively limited mass flow of refrigerant.
It is the primary object of the invention to provide a new and improved cooling system for a vehicle that includes a CO2 type air conditioning system and a coolant system for an engine coolant for the vehicle.
In one form of the invention, a cooling system is provided for a vehicle that includes an air cooled coolant radiator to cool a coolant flow of the vehicle and an air cooled gas cooler to cool a gas flow of a CO2 type air conditioning system of the vehicle. The radiator includes a plurality of coolant tubes to direct the coolant flow through the radiator, and spaces between the coolant tubes to direct a cooling air flow through the radiator. The gas cooler is positioned upstream in an cooling air flow direction with respect to the radiator. The system further includes a gas pre-cooler in heat-conducting contact with at least one of the coolant flow through the radiator and the cooling air flow to allow the gas flow to be cooled thereby.
In one form, the pre-cooler includes an inlet gas conduit connected to the gas cooler to direct the gas flow thereto from the pre-cooler. The inlet gas conduit is positioned downstream of the radiator in the cooling air flow direction to be cooled by the cooling air flow exiting the radiator.
In one form, at least part of the pre-cooler is located in a coolant collecting tank of the radiator to be cooled by the coolant flow in the collecting tank.
In one form, the coolant system further includes an expansion vessel for the coolant flow, and at least part of the pre-cooler is located in the expansion vessel to be cooled by the coolant flow in the expansion vessel.
In one form, the gas cooler includes at least one tube, and the pre-cooler includes at least a portion of the at least one tube extending along and in heat-conducting contact with at least one of the coolant tubes of the radiator. According to one form, the cooling system further includes an air-side fin contacting both the portion of the at least one tube and the at least one of the coolant tubes of the radiator.
In form of the invention, the coolant system is provided for a vehicle and includes an air-cooled coolant radiator to cool a coolant flow of the vehicle, and an air-cooled gas cooler to cool a gas flow of CO2 type air conditioning system of the vehicle. The radiator includes a plurality of coolant tubes to direct the coolant flow through the radiator, and spaces between the coolant tubes to direct a cooling air flow through the radiator. The gas cooler includes an inlet manifold. The system further includes an inlet gas conduit connected to the inlet manifold to direct the gas flow thereto. The inlet gas conduit is positioned downstream of the radiator in the cooling air flow direction to be cooled by the cooling air flow exiting the radiator.
In accordance with one form of the invention, a cooling system is provided for a vehicle and includes an air-cooled coolant radiator to cool a coolant flow of the vehicle, and an air-cooled gas cooler to cool a gas flow of a CO2 type air conditioning system of a vehicle. The radiator includes a coolant collecting tank, and the gas cooler includes an inlet manifold. The cooling system further includes a heat exchanger connected to the inlet manifold to direct the gas flow thereto. The heat exchanger is located in the coolant collecting tank to be cooled by the coolant flow.
In one form of the invention, a cooling system is provided for a vehicle and includes an expansion vessel for a cooling system of the vehicle, and air-cooled coolant radiator for the coolant system of the vehicle, and an air cooled gas cooler to cool a gas flow of a CO2 type air conditioning system of the vehicle. The gas cooler includes an inlet manifold. The system further includes a heat exchanger connected to the inlet manifold to direct the gas flow thereto. The heat exchanger is located in the expansion vessel to be cooled by coolant in the expansion vessel.
In accordance with of one form of the invention, a cooling system is provided for a vehicle and includes an air-cooled coolant radiator to cool a coolant flow of the vehicle, and an air-cooled gas cooler to cool a gas flow of a CO2 type air conditioning system of the vehicle. The radiator includes a plurality of coolant tubes to direct the coolant flow through the radiator, and spaces between the coolant tubes to direct a cooling air flow through the radiator. The gas cooler is positioned upstream in a cooling air flow direction with respect to the radiator, and includes a inlet manifold and at least one tube. At least a portion of the at least one tube extends along and is in heat-conducting contact with at least one of the coolant tubes of the radiator.
In one form of the invention, a method is provided for cooling a gas flow of a CO2 type air conditioning system in a vehicle including an air-cooled gas cooler to cool the gas flow and an air-cooled coolant radiator to cool a coolant flow of the vehicle by transferring heat to a cooling air flow passing through the radiator. The method includes the steps of pre-cooling the gas flow by transferring heat to at least one of the coolant flow and the cooling air flow, and after the pre-cooling step, cooling the gas flow in the gas cooler by transferring heat from the gas flow to the cooling air flow.
Other objects, advantages, aspects, and forms of the invention will be realized by reviewing the entire specification, including the appended claims and drawings.